The subject invention relates to automotive seat assemblies having integral airbags. More precisely, the subject invention relates to the specific characteristics of the seat assembly which ensure a complete and full deployment of the airbag.
Government and automobile industry researches are continuously looking at ways to make can safer. Airbags are frequently installed within the dash board, armrest, and steering wheel of many vehicles to enhance the safety of the vehicle. European Patent No. 0 749 872 illustrates one such example of an airbag in a dash board and European Patent No. 0 733 518 illustrates an example of an airbag disposed within an armrest. Both of these designs form a weakened deployment seam within the plastic material forming the dashboard and armrest. The deployment seam is typically formed on both an inside and outside of the material. Once deficiency with forming the seam on both sides of the material is that this creates a noticeable cut or depression in the dashboard and armrest. As disclosed in the European ""872 patent, the seams are typically formed by inserting a welder into the material itself. This method of forming the seams can significantly reduce the operating life of the welder.
The frequent use of airbags has lead to the thought of installing airbags in other locations within the vehicle. One prominent direction is toward installing airbags directly within a vehicle seat. Primarily, the airbags are installed within a side bolster of the seat such that they provide better head, neck and side protection for the occupant. These airbags are commonly called side impact airbags. Side impact airbags operate much the same fashion as frontal airbags. A crash sensor is often located in a B-pillar of the vehicle which detects a serious impact occurring perpendicular to the side of the vehicle. As appreciated, there is little clearance between the passenger and the outside of the vehicle door. Hence, side impact airbags must inflate much faster than frontal airbags.
The side impact airbags are frequently concealed within the seat by a trim cover material. The trim cover material is typically made up of multiple smaller pieces of material which are sewn together. The airbags break through the sewn seams during deployment. One of the major concerns with seat integrated side impact airbags is achieving successful deployment of the airbag through the proper seam in the trim cover each and every time.
One frequent difficulty associated with side impact airbag deployment is that the airbag deploys through the seam at a wrong angle. This limits the amount of protection available to the passenger and may even injure the passenger. Another problem occurs when the airbag exits through the wrong seam such as through the front or the back of the seat. This may also cause additional injury and may not adequately protect the passenger. In addition, the airbag may not exit the seat at all. In this situation, the airbag balloons within the trim cover material and never breaks the seam.
The deployment problems occur for a number of reasons. The trim cover material typically has an elasticity which works against the braking force the airbag. In addition the trim cover material is secured to a foam pad by either thin wire rods, hog rings, a hook and loop fastener, or a bonding process. None of these manufacturing methods are strong enough to hold the trim cover material to the foam pad when the airbag is being deployed. The airbag will always follow the path of least resistance and may detach the trim cover from the foam pad such that the airbag will wander within the trim cover itself.
One solution contemplated by the prior art is to sew straps into the trim cover and tie the straps to the seat back frame to hold the trim cover material to the foam pad and seat back frame. This solution, however, has a number of deficiencies. Some of the deficiencies are that the straps may be difficult to secure to the frame, it would be difficult to ensure proper attachment and proper taughtness, and the straps may provide unpredictable deployment characteristics.
Accordingly, it is desirable to create a weakened deployment seam within the trim cover material that is the weakest point in the trim cover such that the airbag can predictably break through the trim cover material and fully deploy. The deployment seam must also be strong enough to maintain its integrity during normal use of the seat.
Some solutions have been contemplated by the prior art such as laser cutting and changing the parameters of the stitching. The laser cutting is unreliable in that the particular depth needed is difficult to uniformly achieve. The laser cutting is also time consuming and expensive. Changing the parameters of the stitching along the area of deployment is also difficult to control and expensive to implement.
Ultrasonic welding is a means of fusing pieces of material together and for forming cuts or grooves within both sides of a material. One such example of ultrasonic welding is shown in French Patent No. 2 665 683 which ultrasonically welds thin plastic bags. The known ultrasonic welders, however, have not been modified and thus are not capable of forming seams within relatively thick multilayered pieces of material such as trim cover materials.
An automotive seat assembly is provided with an integrated airbag. The seat assembly comprises a seat cushion and a seat back mounted to the seat cushion. A seat cushion trim cover material covers the seat cushion and a seat back trim cover material covers the seat back. The seat assembly is characterized by a tear seam integrally formed within at least one of the trim cover materials to define a frangible line of weakness within the trim material wherein the airbag will tear trough the tear seam when the airbag is deployed and inflated to a position outside of the seat assembly.
Accordingly, the subject invention provides a weakened tear seam within the trim cover material which is the weakest point in the trim cover such that the airbag can predictably and effectively break through the trim cover material and fully deploy. The tear seam is also strong enough to maintain its integrity during normal use of the seat assembly.